Factors Affecting The Sterilization Efficacy Of Ethylene Oxide

Ethylene oxide (EO) is a highly effective chemical sterilant capable of eliminating all microorganisms, including bacterial spores. It operates on the principle of alkylation rather than oxidation, thereby minimizing damage to sterilized items. Additionally, EO sterilization allows for the use of various packaging materials, facilitating storage and transportation while reducing the risk of cross-contamination—packages can be opened and used directly. In the medical device industry, EO is the preferred sterilization method for the majority of devices packaged in thermoformed trays.

Before discussing the influencing factors, here is a brief overview of the advantages and disadvantages of EO sterilization.

Advantages:

EO is suitable for sterilizing items that cannot withstand high temperatures or moisture. For example, medical thermoformed trays made from materials such as APET and PETG are incompatible with high-temperature sterilization, making EO an excellent alternative.
EO sterilization offers standardized chemical and biological monitoring methods, enabling effective quality control and timely detection of sterilization failures.
In addition to the benefits mentioned above, EO exhibits strong penetration capabilities, making it effective for sterilizing hard-to-reach areas, such as long, narrow catheters that are challenging to sterilize using other methods. In such cases, EO or irradiation remain the viable options.

Disadvantages:

Firstly, EO is toxic and a suspected carcinogen. It is essential to maintain its concentration in the workplace air below nationally mandated limits.
Secondly, EO is flammable and explosive, requiring the use of secure sterilizers and adherence to safe handling and storage practices.
Finally, the entire EO sterilization cycle is relatively lengthy, as additional aeration time is needed to eliminate residual EO.

Factors Affecting the Sterilization Efficacy of Ethylene Oxide

The key factors can be summarized as follows:

Concentration is the most critical factor, with the typical range being 450–1200 mg/L.
The sterilizing effect of EO intensifies with higher temperatures, and the commonly used sterilization temperature ranges from 35°C to 60°C.
The moisture content of the items to be sterilized, the dryness of the microorganisms themselves, and the relative humidity of the sterilization environment (typically 45%–75%, with exposure times of 105–300 minutes) all significantly impact EO’s efficacy.

These factors directly determine the success or failure of sterilization. Only when all four key factors are properly balanced can consistent sterilization quality be ensured.

It is important to note that although EO has strong penetrating ability, capable of passing through micropores to reach the innermost areas of items, its penetration varies depending on the density of the materials. Taking medical thermoformed trays as an example—when used as primary packaging for medical devices—design considerations should extend beyond functionality, seal integrity, safety, and aesthetics. It is equally crucial to预留 EO sterilization channels during the design phase, ensuring that EO gas can penetrate effectively during sterilization to achieve the intended results.

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Factors Affecting the Sterilization Efficacy of Ethylene Oxide

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